The invention relates to the identification and quantitation of a central nervous system (CNS) protein in cerebral spinal fluid and amniotic fluid.
Field of Art and Discussion of Related Art
Certain CNS proteins are of interest as markers and trackers of brain pathophysiology, especially in the areas of synaptogenesis and synaptic vesicle release. Neurotransmitter release is, however, a complicated process involving many different proteins (Nature 355: 409-415, 1992), some of which are SNAP-25 (synaptosomal associated protein-25 kDa), VAMP/synaptobrevin (1,2), syntaxin (1a, 1b), neurexin (1,2), synapsin (1,2), and synaptophysin.
The understanding of normal brain physiology is moving at great speed. One area that is especially important to diagnosing and treating mental illnesses is the pathway for release of neurotransmitters. In this process proteins called vesicular snares (V-snares) attach to plasma membrane and release neurotransmitter (Nature 335: 409-415, 1992). One T-snare that is associated with mental illness is SNAP-25. This protein is found predominately in brain tissue of neuronal origin (Molecular Brain Research 1: 1-16, 1986). The other major brain tissue (glial cells) is non-neuronal and SNAP-25 has not been associated with this tissue. SNAP-25 in monomeric form is 25 kDa, but can be found in vivo as a dimer, or associated with other synaptic proteins (e.g. syntaxins).
SNAP-25 appears to be particularly important in the pathophysiology of schizophrenia and other major brain disorders, because of its known dual role in synaptic vesicle release and synaptogenesis (J. Neuroscience 12: 2865-2874, 1992; PNAS USA 92: 1510-1514, 1995). Also, it has been shown that both SNAP-25 and GAP-43 (Mol. and Chem. Neuropath. 23: 1-11, 1994) have altered levels in post mortem brains of schizophrenic patients. These or other proteins involved with synaptic vesicle release and synaptogenesis may be strongly associated with brain function and behavior.
Mental illness (as defined e.g., by Andreasen and Black (Andreasen, N. C., Black, D. W. Introductory textbook of psychiatry 1991, American Psychiatric Press, Inc.) has a profound effect on public health, but psychiatry has had difficulty developing biological assays to diagnosis and follow them. Neuroscientific interest has particularly been aroused by the possibility of correlating levels of these and other CNS proteins with specific brain pathologies and with different stages of illness, such as identifying brain changes in schizophrenia and other major brain disorders, such as Alzheimer's disease and clinical depression. Although impressive gains have been made in neuroimaging and brain electrophysiology, molecular and cellular markers of schizophrenia and other brain disorders have lagged. There are no consistent known biochemical markers for schizophrenia pathophysiology, and none that reflect effectiveness of a course of treatment. There is a lack of complete animal models of schizophrenia and lack of in vitro assays for physiologically-relevant neuronal proteins. Further, obtaining material to perform biological assays has been a constant problem in schizophrenia and other brain disorder research. Peripheral assays including platelet levels, peripheral nerve biopsy, and neurohormone levels have not yielded informative data. More central assays such as estimating neurotransmitter levels in cerebral spinal fluid (CSF) have been only marginally more informative (Ann, Clin. Biochem 27: 425-435, 1990). Direct methods of studying neuronal tissues such as brain biopsies are prohibitively destructive due to loss of brain tissue. These impediments have limited the most potentially informative studies to post-mortem studies.
These difficulties have hindered research on the identification of neuronal proteins and their roles in the molecular pathways involved in pathological changes in the brain.